Trading signals now expire in 18 months, down from years, as AI adoption accelerates competitive decay

AI adoption across 70% of institutional trading desks has halved the lifespan of profitable trading signals to 18 months from 5–7 years, according to mathematical modeling of alpha decay. Signal crowding, performative erosion, and competitive pressure all compress returns simultaneously. This shift erodes the foundational economics of quantitative strategies and challenges multi-year portfolio construction models that many asset managers still rely on.